The atypical CDK activator Spy1 regulates the intrinsic DNA damage response and is dependent upon p53 to inhibit apoptosis

Targeting cyclin-dependent kinase 2 (CDK2) interactions with cyclins and Speedy 1 (Spy1) for cancer and male contraception

The review discusses progress in discovering cyclin-dependent kinase 2 (CDK2) inhibitors for cancer treatment and their potential for male contraception. It summarizes first-, second-, and third-generation CDK inhibitors and selective CDK2 inhibitors currently in clinical trials for cancer. Novel strategies to discover allosteric inhibitors, covalent inhibitors, and degraders are also discussed.

Phosphorus Metabolism-Related Genes Serve as Novel Biomarkers for Predicting Prognosis in Bladder Cancer: A Bioinformatics Analysis

Background

Phosphorus metabolism might be associated with tumor initiation and progression. We aimed to screen out the phosphorus metabolism genes related to bladder cancer and construct a clinical prognosis model.

Methods

The dataset used for the analysis was obtained from TCGA database. GO and KEGG enrichment analyses were subsequently applied to differentially expressed genes. Consensus clustering was utilized, and different clusters of the tumor immune microenvironment and other features were compared. The phosphorus metabolism-related genes involved in prognosis were screened out by univariate Cox regression, LASSO regression and multivariate Cox regression analysis, and a nomogram was constructed. The performance of the nomogram was validated using TCGA dataset and the GEO dataset, respectively.

Results

Overall, 405 phosphorus metabolism-related differentially expressed genes from TCGA database were identified, which were associated with phosphorylation, cell proliferation, leukocyte activation, and signaling pathways. Two clusters were obtained by consistent clustering. After tumor immune microenvironment analysis, significant differences in immune cell infiltration between cluster 1 and cluster 2 were found. Four phosphorus metabolism-related genes (LIME1, LRP8, SPDYA, and MST1R) were associated with the prognosis of bladder cancer (BLCA) patients. We built a prognostic model and visualized the model as a nomogram. Calibration curves demonstrated the performance of this nomogram, in agreement with that shown by the ROC curves.

Conclusion

We successfully identified four phosphorus metabolism-related genes associated with prognosis, providing potential targets for biomarkers and therapeutics. A nomogram based on these genes was developed. Nevertheless, this study is based on bioinformatics, and experimental validation remains essential.

Atypical cell cycle regulation promotes mammary stem cell expansion during mammary development and tumourigenesis

BACKGROUND

The cell cycle of mammary stem cells must be tightly regulated to ensure normal homeostasis of the mammary gland to prevent abnormal proliferation and susceptibility to tumorigenesis. The atypical cell cycle regulator, Spy1 can override cell cycle checkpoints, including those activated by the tumour suppressor p53 which mediates mammary stem cell homeostasis. Spy1 has also been shown to promote expansion of select stem cell populations in other developmental systems. Spy1 protein is elevated during proliferative stages of mammary gland development, is found at higher levels in human breast cancers, and promotes susceptibility to mammary tumourigenesis when combined with loss of p53. We hypothesized that Spy1 cooperates with loss of p53 to increase susceptibility to tumour initiation due to changes in susceptible mammary stem cell populations during development and drives the formation of more aggressive stem like tumours.

METHODS

Using a transgenic mouse model driving expression of Spy1 within the mammary gland, mammary development and stemness were assessed. These mice were intercrossed with p53 null mice to study the tumourigenic properties of Spy1 driven p53 null tumours, as well as global changes in signaling via RNA sequencing analysis.

RESULTS

We show that elevated levels of Spy1 leads to expansion of mammary stem cells, even in the presence of p53, and an increase in mammary tumour formation. Spy1-driven tumours have an increased cancer stem cell population, decreased checkpoint signaling, and demonstrate an increase in therapy resistance. Loss of Spy1 decreases tumor onset and reduces the cancer stem cell population.

CONCLUSIONS

This data demonstrates the potential of Spy1 to expand mammary stem cell populations and contribute to the initiation and progression of aggressive, breast cancers with increased cancer stem cell populations.

SPY1 inhibits neuronal ferroptosis in amyotrophic lateral sclerosis by reducing lipid peroxidation through regulation of GCH1 and TFR1

Ferroptosis is an iron-dependent cell death with the accumulation of lipid peroxidation and dysfunction of antioxidant systems. As the critical regulator, glutathione peroxidase 4 (GPX4) has been demonstrated to be down-regulated in amyotrophic lateral sclerosis (ALS). However, the mechanism of ferroptosis in ALS remains unclear. In this research, bioinformatics analysis revealed a high correlation between ALS, ferroptosis, and Speedy/RINGO cell cycle regulator family member A (SPY1). Lipid peroxidation of ferroptosis in hSOD1G93A cells and mice was generated by TFR1-imported excess free iron, decreased GSH, mitochondrial membrane dysfunction, upregulated ALOX15, and inactivation of GCH1, GPX4. SPY1 is a "cyclin-like" protein that has been proved to enhance the viability of hSOD1^G93A cells by inhibiting DNA damage. In our study, the decreased expression of SPY1 in ALS was resulted from unprecedented ubiquitination degradation mediated by MDM2 (a nuclear-localized E3 ubiquitin ligase). Further, SPY1 was identified as a novel ferroptosis suppressor via alleviating lipid peroxidation produced by dysregulated GCH1/BH4 axis (a resistance axis of ferroptosis) and transferrin receptor protein 1 (TFR1)-induced iron. Additionally, neuron-specific overexpression of SPY1 significantly delayed the occurrence and prolonged the survival in ALS transgenic mice through the above two pathways. These results suggest that SPY1 is a novel target for both ferroptosis and ALS.

Golgi Complex: A Signaling Hub in Cancer

The Golgi Complex is the central hub in the endomembrane system and serves not only as a biosynthetic and processing center but also as a trafficking and sorting station for glycoproteins and lipids. In addition, it is an active signaling hub involved in the regulation of multiple cellular processes, including cell polarity, motility, growth, autophagy, apoptosis, inflammation, DNA repair and stress responses. As such, the dysregulation of the Golgi Complex-centered signaling cascades contributes to the onset of several pathological conditions, including cancer. This review summarizes the current knowledge on the signaling pathways regulated by the Golgi Complex and implicated in promoting cancer hallmarks and tumor progression.

Cyclin-like proteins tip regenerative balance in the liver to favour cancer formation

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. A variety of factors can contribute to the onset of this disease, including viral infection, obesity, alcohol abuse and non-alcoholic fatty liver disease (NAFLD). These stressors predominantly introduce chronic inflammation leading to liver cirrhosis and finally the onset of HCC; however, approximately 20% of HCC cases arise in the absence of cirrhosis via a poorly defined mechanism. The atypical cyclin-like protein Spy1 is capable of overriding cell cycle checkpoints, promoting proliferation and has been implicated in HCC. We hypothesize that Spy1 promotes sustained proliferation making the liver more susceptible to accumulation of deleterious mutations, leading to the development of non-cirrhotic HCC. We report for the first time that elevation of Spy1 within the liver of a transgenic mouse model leads to enhanced spontaneous liver tumourigenesis. We show that the abundance of Spy1 enhanced fat deposition within the liver and decreased the inflammatory response. Interestingly, Spy1 transgenic mice have a significant reduction in fibrosis and sustained rates of hepatocyte proliferation, and endogenous levels of Spy1 are downregulated during the normal fibrotic response. Our results provide support that abnormal regulation of Spy1 protein drives liver tumorigenesis in the absence of elevated fibrosis and, hence, may represent a potential mechanism behind non-cirrhotic HCC. This work may implicate Spy1 as a prognostic indicator and/or potential target in the treatment of diseases of the liver, such as HCC. The cyclin-like protein Spy1 enhances lipid deposition and reduces fibrosis in the liver. Spy1 also promotes increased hepatocyte proliferation and onset of non-cirrhotic hepatocellular carcinoma (HCC). Thus, Spy1 may be used as a potential target in the treatment of HCC.

Speedy/RINGO protein interacts with ERK/MAPK and PI3K/AKT pathways in SH-SY5Y neuroblastoma cells

Abnormal activity of ERK/MAPK and PI3K/AKT pathways is one of the most important factors for the development of many cancer types including neuroblastoma cancer. Apart from these two pathways, some cell cycle regulators such as Speedy/RINGO also contribute to neuroblastoma development. There is data reinforcing the possible communication of the components of ERK/MAPK and PI3K/AKT pathways in carcinogenic process. In addition to this, there are studies about the direct/indirect interaction of Speedy/RINGO with these pathways in different cell types other than neuroblastoma. However, there is not any study available showing the interaction of Speedy/RINGO with both pathways in neuroblastoma cells. Therefore, the aim of this study is to determine the possible effect of Speedy/RINGO on PI3K/AKT and ERK/MAPK pathways in SH-SY5Y neuroblastoma cells. For this aim, Speedy/RINGO was silenced by siRNA technique to analyze the effects of direct inhibition of Speedy/RINGO on these pathways. Results showed that Speedy/RINGO silencing caused a significant decrease in MEK1/2 expression and AKT phosphorylation. Afterward, MEK1/2 was inhibited using a specific inhibitor U0126. Data reveal a corresponding decrease in the Speedy/RINGO expression and AKT phosphorylation indicating a reciprocal interaction between ERK/MAPK and Speedy/RINGO. In addition, MTS analysis showed that both ERK/MAPK inhibition and Speedy/RINGO silencing significantly reduced the viability of SH-SY5Y cells. This study provides information about a possible interaction of Speedy/RINGO with PI3K/AKT and ERK/MAPK pathways in SH-SY5Y cells for the first time. It will not only help to better understand the cancer-prone interactions of these pathways but also enable us to identify the appropriate molecular targets for developing efficient treatment strategies.

RINGO/Speedy proteins, a family of non-canonical activators of CDK1 and CDK2

Cyclin-dependent kinases (CDKs) require the binding to a regulatory subunit to acquire enzymatic activity, and cyclins are the canonical CDK activators. However, there are specific situations in which CDKs can be activated by non-cyclin proteins that are less characterized. This review focuses on the family of RINGO/Speedy proteins, which have no sequence amino acid homology to cyclins but can bind to and activate CDK1 and CDK2. Interestingly, RINGO/Speedy proteins can activate CDKs under conditions in which CDK-cyclin complexes would not be active, and there is evidence that RINGO/Speedy-activated CDKs can phosphorylate different sites than the cyclin-activated CDKs. RINGO/Speedy proteins were originally described in Xenopus oocytes, but their roles in mammalian cells have also been addressed. We will summarize the properties of RINGO/Speedy proteins and how they trigger CDK activation, and discuss recent studies that characterized their physiological functions. In particular, studies using genetically modified mice have shown that RingoA, also known as Spy1, plays a key role in meiosis regulation. Emerging evidence also suggests a potential role for RingoA/Spy1 in cancer.

The atypical cyclin-like protein Spy1 overrides p53-mediated tumour suppression and promotes susceptibility to breast tumourigenesis

Background

Breast cancer is the most common cancer to affect women and one of the leading causes of cancer-related deaths. Proper regulation of cell cycle checkpoints plays a critical role in preventing the accumulation of deleterious mutations. Perturbations in the expression or activity of mediators of cell cycle progression or checkpoint activation represent important events that may increase susceptibility to the onset of carcinogenesis. The atypical cyclin-like protein Spy1 was isolated in a screen for novel genes that could bypass the DNA damage response. Clinical data demonstrates that protein levels of Spy1 are significantly elevated in ductal and lobular carcinoma of the breast. We hypothesized that elevated Spy1 would override protective cell cycle checkpoints and support the onset of mammary tumourigenesis.

Methods

We generated a transgenic mouse model driving expression of Spy1 in the mammary epithelium. Mammary development, growth characteristics and susceptibility to tumourigenesis were studied. In vitro studies were conducted to investigate the relationship between Spy1 and p53.

Results

We found that in the presence of wild-type p53, Spy1 protein is held ‘in check’ via protein degradation, representing a novel endogenous mechanism to ensure protected checkpoint control. Regulation of Spy1 by p53 is at the protein level and is mediated in part by Nedd4. Mutation or abrogation of p53 is sufficient to allow for accumulation of Spy1 levels resulting in mammary hyperplasia. Sustained elevation of Spy1 results in elevated proliferation of the mammary gland and susceptibility to tumourigenesis.

Conclusions

This mouse model demonstrates for the first time that degradation of the cyclin-like protein Spy1 is an essential component of p53-mediated tumour suppression. Targeting cyclin-like protein activity may therefore represent a mechanism of re-sensitizing cells to important cell cycle checkpoints in a therapeutic setting.

Exposure to environmental radionuclides is associated with altered metabolic and immunity pathways in a wild rodent

Wildlife inhabiting environments contaminated by radionuclides face putative detrimental effects of exposure to ionizing radiation, with biomarkers such as an increase in DNA damage and/or oxidative stress commonly associated with radiation exposure. To examine the effects of exposure to radiation on gene expression in wildlife, we conducted a de novo RNA sequencing study of liver and spleen tissues from a rodent, the bank vole Myodes glareolus. Bank voles were collected from the Chernobyl Exclusion Zone (CEZ), where animals were exposed to elevated levels of radionuclides, and from uncontaminated areas near Kyiv, Ukraine. Counter to expectations, we did not observe a strong DNA damage response in animals exposed to radionuclides, although some signs of oxidative stress were identified. Rather, exposure to environmental radionuclides was associated with upregulation of genes involved in lipid metabolism and fatty acid oxidation in the livers - an apparent shift in energy metabolism. Moreover, using stable isotope analysis, we identified that fur from bank voles inhabiting the CEZ had enriched isotope values of nitrogen: such an increase is consistent with increased fatty acid metabolism, but also could arise from a difference in diet or habitat between the CEZ and elsewhere. In livers and spleens, voles inhabiting the CEZ were characterized by immunosuppression, such as impaired antigen processing, and activation of leucocytes involved in inflammatory responses. In conclusion, exposure to low dose environmental radiation impacts pathways associated with immunity and lipid metabolism, potentially as a stress-induced coping mechanism.

R-Spondin-2 Is Upregulated in Idiopathic Pulmonary Fibrosis and Affects Fibroblast Behavior

Idiopathic pulmonary fibrosis (IPF) is characterized by the expansion of the myofibroblast population, excessive extracellular matrix accumulation, and destruction of the lung parenchyma. The R-spondin family (RSPO) comprises a group of proteins essential for development. Among them, RSPO2 is expressed primarily in the lungs, and its mutations cause severe defects in the respiratory tract. Interestingly, RSPO2 participates in the canonical Wingless/int1 pathway, a critical route in the pathogenesis of IPF. Thus, the aim of this study was to examine the expression and putative role of RSPO2 in this disease. We found that RSPO2 and its receptor leucine-rich G protein-coupled receptor 6 were upregulated in IPF lungs, where they localized primarily in fibroblasts and epithelial cells. Stimulation of IPF and normal lung fibroblasts with recombinant human RSPO2 resulted in the deregulation of numerous genes, although the transcriptional response was essentially distinct. In IPF fibroblasts, RSPO2 stimulation induced the up- or downregulation of several genes involved in the Wingless/int1 pathway (mainly from noncanonical signaling). In both normal and IPF fibroblasts, RSPO2 modifies the expression of genes implicated in several pathways, including the cell cycle and apoptosis. In accordance with gene expression, the stimulation of normal and IPF fibroblasts with RSPO2 significantly reduced cell proliferation and induced cell death. RSPO2 also inhibited collagen production and increased the expression of matrix metalloproteinase 1. Silencing RSPO2 with shRNA induced the opposite effects. Our findings demonstrate, for the first time to our knowledge, that RSPO2 is upregulated in IPF, where it appears to have an antifibrotic role.

Cyclin B1/CDK1-regulated mitochondrial bioenergetics in cell cycle progression and tumor resistance

A mammalian cell houses two genomes located separately in the nucleus and mitochondria. During evolution, communications and adaptations between these two genomes occur extensively to achieve and sustain homeostasis for cellular functions and regeneration. Mitochondria provide the major cellular energy and contribute to gene regulation in the nucleus, whereas more than 98% of mitochondrial proteins are encoded by the nuclear genome. Such two-way signaling traffic presents an orchestrated dynamic between energy metabolism and consumption in cells. Recent reports have elucidated the way how mitochondrial bioenergetics synchronizes with the energy consumption for cell cycle progression mediated by cyclin B1/CDK1 as the communicator. This review is to recapitulate cyclin B1/CDK1 mediated mitochondrial activities in cell cycle progression and stress response as well as its potential link to reprogram energy metabolism in tumor adaptive resistance. Cyclin B1/CDK1-mediated mitochondrial bioenergetics is applied as an example to show how mitochondria could timely sense the cellular fuel demand and then coordinate ATP output. Such nucleus-mitochondria oscillation may play key roles in the flexible bioenergetics required for tumor cell survival and compromising the efficacy of anti-cancer therapy. Further deciphering the cyclin B1/CDK1-controlled mitochondrial metabolism may invent effect targets to treat resistant cancers.

High Spy1 expression predicts poor prognosis in colorectal cancer

Background

Spy1 (SPDYA) is a new discovered cell cycle protein capable of promoting cell proliferation dependent on cyclin-dependent kinase-2 activation. However, to the best of our knowledge, the expression of Spy1 in colorectal cancer (CRC) tissues remains virtually unknown.

Materials and methods

In this retrospective study, we investigated the mRNA and protein expression levels of Spy1 in CRC tissues and corresponding non-cancerous tissues with the analyses of quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry. In our research, the prognostic significances of Spy1 expression were further explored by univariate and multivariate survival analyses of 203 patients who were followed up.

Results

The results demonstrated that the levels of Spy1 mRNA were significantly higher in CRC tissues compared with corresponding non-cancerous tissues (p=0.0002). The results of immunohistochemistry demonstrated that the expressions of Spy1 were significantly associated with clinicopathological parameters, including T stage (χ²=7.126, p=0.028) and TNM stage (χ²=9.461, p=0.009). Kaplan-Meier analysis results indicated that high Spy1 expression (HR=2.573, p<0.001) and TNM stage (HR=1.494, p=0.011) were independent factors to predict poor prognosis for patients with CRC.

Conclusion

We concluded that high Spy1 expression is significantly associated with unfavorable prognosis in CRC and could serve as a potential prognostic marker in clinical diagnosis of CRC.

Structural basis of divergent cyclin-dependent kinase activation by Spy1/RINGO proteins

Cyclin-dependent kinases (Cdks) are principal drivers of cell division and are an important therapeutic target to inhibit aberrant proliferation. Cdk enzymatic activity is tightly controlled through cyclin interactions, posttranslational modifications, and binding of inhibitors such as the p27 tumor suppressor protein. Spy1/RINGO (Spy1) proteins bind and activate Cdk but are resistant to canonical regulatory mechanisms that establish cell-cycle checkpoints. Cancer cells exploit Spy1 to stimulate proliferation through inappropriate activation of Cdks, yet the mechanism is unknown. We have determined crystal structures of the Cdk2-Spy1 and p27-Cdk2-Spy1 complexes that reveal how Spy1 activates Cdk. We find that Spy1 confers structural changes to Cdk2 that obviate the requirement of Cdk activation loop phosphorylation. Spy1 lacks the cyclin-binding site that mediates p27 and substrate affinity, explaining why Cdk-Spy1 is poorly inhibited by p27 and lacks specificity for substrates with cyclin-docking sites. We identify mutations in Spy1 that ablate its ability to activate Cdk2 and to proliferate cells. Our structural description of Spy1 provides important mechanistic insights that may be utilized for targeting upregulated Spy1 in cancer.

Effects of pyrrolidine dithiocarbamate on proliferation and nuclear factor-κB activity in autosomal dominant polycystic kidney disease cells

BACKGROUND

Pyrrolidine dithiocarbamate (PDTC) reduces renal cyst growth in a rodent model of polycystic kidney disease (PKD) but the mechanism of action is not clear. Here, we investigated the hypothesis that PDTC reduces the proliferation of cystic epithelial cells in vitro in a nuclear factor (NF)-κB-dependent manner.

METHODS

Immortalized autosomal dominant PKD (ADPKD) cells that are heterozygous (WT9-7) and homozygous (WT-9-12) for a truncating Pkd1 mutation, and immortalized normal human tubular cells (HK-2), were exposed to NF-κB-inducing agents with or without PDTC. Cell proliferation and apoptosis were assessed by bromodeoxyuridine assay and Annexin V flow cytometry, respectively. NF-κB activity was assessed by luciferase reporter assay and western blotting for nuclear p65, p50, and RelB subunits and cytoplasmic phosphorylated-IκBα.

RESULTS

Serum-induced proliferation was similar in all cell lines over 72 h. PDTC demonstrated anti-proliferative effects that were delayed in ADPKD cells compared to HK-2. Basal NF-κB-dependent luciferase reporter activity was lower in ADPKD cells compared to normal cells. Classical NF-κB stimulants, lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α, increased NF-κB luciferase activity in HK-2, whereas in PKD cell lines, NF-κB activity was only induced by TNF-α. However, neither stimulant altered proliferation in any cell line. PDTC reduced TNF-α-stimulated NF-κB activity in HK-2 only.

CONCLUSIONS

PDTC reduced proliferation in ADPKD cells but did not consistently alter NF-κB activation, suggesting that other signalling pathways are likely to be involved in its ability to attenuate renal cyst growth in vivo.

Spy1 induces de-ubiquitinating of RIP1 arrest and confers glioblastoma's resistance to tumor necrosis factor (TNF-α)-induced apoptosis through suppressing the association of CLIPR-59 and CYLD

Glioblastoma multiforme (GBM), a grade-IV glioma, is resistant to TNF-α induced apoptosis. CLIPR-59 modulates ubiquitination of RIP1, thus promoting Caspase-8 activation to induce apoptosis by TNF-α. Here we reported that CLIPR-59 was down-regulated in GBM cells and high-grade glioma tumor samples, which was associated with decreased cancer-free survival. In GBM cells, CLIPR-59 interacts with Spy1, resulting in its decreased association with CYLD, a de-ubiquitinating enzyme. Moreover, experimental reduction of Spy1 levels decreased GBM cells viability, while increased the lysine-63-dependent de-ubiquitinating activity of RIP1 via enhancing the binding ability of CLIPR-59 and CYLD in GBM, thus promoting Caspase-8 and Caspase-3 activation to induce apoptosis by TNF-α. These findings have identified a novel Spy1-CLIPR-59 interplay in GBM cell's resistance to TNF-α-induced apoptosis revealing a potential target in the intervention of malignant brain tumors.

Neuroprotective strategies against calpain-mediated neurodegeneration

Calpains are calcium-dependent proteolytic enzymes that have deleterious effects on neurons upon their pathological over-activation. According to the results of numerous studies to date, there is no doubt that abnormal calpain activation triggers activation and progression of apoptotic processes in neurodegeneration, leading to neuronal death. Thus, it is very crucial to unravel all the aspects of calpain-mediated neurodegeneration in order to protect neurons through eliminating or at least minimizing its lethal effects. Protecting neurons against calpain-activated apoptosis basically requires developing effective, reliable, and most importantly, therapeutically applicable approaches to succeed. From this aspect, the most significant studies focusing on preventing calpain-mediated neurodegeneration include blocking the N-methyl-d-aspartate (NMDA)-type glutamate receptor activities, which are closely related to calpain activation; directly inhibiting calpain itself via intrinsic or synthetic calpain inhibitors, or inhibiting its downstream processes; and utilizing the neuroprotectant steroid hormone estrogen and its receptors. In this review, the most remarkable neuroprotective strategies for calpain-mediated neurodegeneration are categorized and summarized with respect to their advantages and disadvantages over one another, in terms of their efficiency and applicability as a therapeutic regimen in the treatment of neurodegenerative diseases.

The atypical cell cycle regulator Spy1 suppresses differentiation of the neuroblastoma stem cell population

Neuroblastoma is an aggressive pediatric cancer originating embryonically from the neural crest. The heterogeneity of the disease, as most solid tumors, complicates diagnosis and treatment. In neuroblastoma this heterogeneity is well represented in both primary tumours and derived cell lines and has been shown to be driven by a population of stem-like tumour initiating cells. Resolving the molecular mediators driving the division of this population of cells may indicate effective therapeutic options for neuroblastoma patients. This study has determined that the atypical cyclin-like protein Spy1, recently indicated in driving symmetric division of glioma stem cells, is a critical factor in the stem-like properties of neuroblastoma tumor initiating cell populations. Spy1 activates Cyclin Dependent Kinases (CDK) in a manner that is unique from classical cyclins. Hence this discovery may represent an important opportunity to design CDK inhibitor drugs to uniquely target subpopulations of cells within these aggressive neural tumours.

Identification of male gametogenesis expressed genes from the scallop Nodipecten subnodosus by suppressive subtraction hybridization and pyrosequencing

Despite the great advances in sequencing technologies, genomic and transcriptomic information for marine non-model species with ecological, evolutionary, and economical interest is still scarce. In this work we aimed to identify genes expressed during spermatogenesis in the functional hermaphrodite scallop Nodipecten subnodosus (Mollusca: Bivalvia: Pectinidae), with the purpose of obtaining a panel of genes that would allow for the study of differentially transcribed genes between diploid and triploid scallops in the context of meiotic arrest and reproductive sterility. Because our aim was to isolate genes involved in meiosis and other testis maturation-related processes, we generated suppressive subtractive hybridization libraries of testis vs. inactive gonad. We obtained 352 and 177 ESTs by clone sequencing, and using pyrosequencing (454-Roche) we maximized the identified ESTs to 34,276 reads. A total of 1,153 genes from the testis library had a blastx hit and GO annotation, including genes specific for meiosis, spermatogenesis, sex-differentiation, and transposable elements. Some of the identified meiosis genes function in chromosome pairing (scp2, scp3), recombination and DNA repair (dmc1, rad51, ccnb1ip1/hei10), and meiotic checkpoints (rad1, hormad1, dtl/cdt2). Gene expression analyses in different gametogenic stages in both sexual regions of the gonad of meiosis genes confirmed that the expression was specific or increased towards the maturing testis. Spermatogenesis genes included known testis-specific ones (kelch-10, shippo1, adad1), with some of these known to be associated to sterility. Sex differentiation genes included one of the most conserved genes at the bottom of the sex-determination cascade (dmrt1). Transcript from transposable elements, reverse transcriptase, and transposases in this library evidenced that transposition is an active process during spermatogenesis in N. subnodosus. In relation to the inactive library, we identified 833 transcripts with functional annotation related to activation of the transcription and translation machinery, as well as to germline control and maintenance.

Temporal-spatial expressions of Spy1 in rat sciatic nerve after crush

As a novel cell cycle protein, Spy1 enhances cell proliferation, promotes the G1/S transition as well as inhibits apoptosis in response to UV irradiation. Spy1 levels are tightly regulated during mammary development, and overexpression of Spy1 accelerates tumorigenesis in vivo. But little is known about the role of Spy1 in the pathological process of damage and regeneration of the peripheral nervous system. Here we established a rat sciatic nerve crush (SNC) model to examine the spatiotemporal expression of Spy1. Spy1 expression was elevated gradually after sciatic nerve crush and peaked at day 3. The alteration was due to the increased expression of Spy1 in axons and Schwann cells after SNC. Spy1 expression correlated closely with Schwann cells proliferation in sciatic nerve post injury. Furthermore, Spy1 largely localized in axons in the crushed segment, but rarely co-localized with GAP43. These findings suggested that Spy1 participated in the pathological process response to sciatic nerve injury and may be associated with Schwann cells proliferation and axons regeneration.

Cooperative effects of Akt-1 and Raf-1 on the induction of cellular senescence in doxorubicin or tamoxifen treated breast cancer cells

Escape from cellular senescence induction is a potent mechanism for chemoresistance. Cellular senescence can be induced in breast cancer cell lines by the removal of estrogen signaling with tamoxifen or by the accumulation of DNA damage induced by the chemotherapeutic drug doxorubicin. Long term culturing of the hormone-sensitive breast cancer cell line MCF-7 in doxorubicin (MCF-7/DoxR) reduced the ability of doxorubicin, but not tamoxifen, to induce senescence. Two pathways that are often upregulated in chemo- and hormonal-resistance are the PI3K/PTEN/Akt/mTOR and Ras/Raf/MEK/ERK pathways. To determine if active Akt-1 and Raf-1 can influence drug-induced senescence, we stably introduced activated ΔAkt-1(CA) and ΔRaf-1(CA) into drug-sensitive and doxorubicin-resistant cells. Expression of a constitutively-active Raf-1 construct resulted in higher baseline senescence, indicating these cells possessed the ability to undergo oncogene-induced-senescence. Constitutive activation of the Akt pathway significantly decreased drug-induced senescence in response to doxorubicin but not tamoxifen in MCF-7 cells. However, constitutive Akt-1 activation in drug-resistant cells containing high levels of active ERK completely escaped cellular senescence induced by doxorubicin and tamoxifen. These results indicate that up regulation of the Ras/PI3K/PTEN/Akt/mTOR pathway in the presence of elevated Ras/Raf/MEK/ERK signaling together can contribute to drug-resistance by diminishing cell senescence in response to chemotherapy. Understanding how breast cancers containing certain oncogenic mutations escape cell senescence in response to chemotherapy and hormonal based therapies may provide insights into the design of more effective drug combinations for the treatment of breast cancer.